There are many applications in data processing which require the formation of a product signal. The data processing arts are replete with multiplication circuits and methods which are particularly adaptable for use in various of these contexts. Thus, for example, there are multiplier circuits which are particularly well adapted for performing the multiplication of data signals from each of two serial data streams. In other applications, however, it is necessary to form the product of signals, one of which is presented in a serial data stream and the other of which is presented in parallel form. Such circuits are used in digital filtering, as described, for example, in Jackson et al, "An Approach to the Implementation of Digital Filters," IEEE Transactions on Audio and Electroacoustics, Vol. AU-16, No. 3, September, 1968.
In general, it has been found convenient in systems including serial adders to represent operands applied to such systems in 2's complement form. However, the properties of 2's complement numbers are such that prior art serial multipliers cannot conveniently process operands in that form. Systems, then, which include both serial adders and serial multipliers, such as digital filters, have been necessarily more complex to permit the multiplication of operands in 2's complement form. It is therefore an object of the present invention to provide a simplified multiplier for processing serial operands in 2's complement form.
It is also of concern that serial multipliers of the type considered herein be substantially modular in order to permit their construction by economical batch fabrication techniques. Prior art multipliers for processing serial 2's complement data typically require significant modifications which adversely affect their modularity and, hence, the economics of their manufacture. It is therefore an object of the present invention to provide serial multipliers for processing 2's complement numbers which multipliers are substantially modular.